Project Summary/Abstract Nearly half of the people living with HIV (PLWH) in the United States were aged 50 years or older in 2016, a figure that is expected to rise to 73% by 2030. Given the combined risk factors associated with both age and HIV that may impact the brain, older PLWH are at a higher risk for neurocognitive problems than their HIV- uninfected counterparts. Despite vast heterogeneity in the way neurocognitive impairment is operationalized in HIV as well as in early Alzheimer's disease and related dementias (ADRD) (i.e., mild cognitive impairment [MCI]), research using consistent methods indicate that PLWH are at a higher risk for MCI. Estimates suggest PLWH may be as much as seven times more likely to develop MCI than those without HIV. MCI in HIV is associated with poorer everyday functioning and lower quality of life. Given the known risk for conversion of MCI to ADRD in the general population, research is warranted to understand protective lifestyle factors that may inform non-pharmacological intervention strategies to ultimately aid PLWH in avoiding or delaying MCI. In the larger aging literature, physical activity and dietary approaches are protective factors against MCI. The field of aging with HIV has historically focused on risk factors in this population, thus little is known on protective lifestyle factors to cognitive health in PLWH. There is a need for ecologically-valid, observational research examining the association of lifestyle factors and neurocognitive function in real-world contexts using comprehensive and gold-standard methods in diverse samples of PLWH. The current study is uniquely positioned to address such gaps in the science, by leveraging the existing multi-site PROSPER-HIV study (R01-NR-018391) focused on the association between physical activity, diet, and HIV symptoms in PLWH by adding a collection of neurocognitive function assessments to this cohort. Specifically, in 200 PLWH > 40 years of age, we will describe the: 1) association between objectively-measured physical activity patterns (intensity, duration, and frequency) and neurocognitive functioning (individual cognitive domains, global cognitive function, and MCI prevalence), and 2) association between an anti-inflammatory dietary pattern and neurocognitive functioning. This work will identify granular relationships between these lifestyle factors and neurocognitive function, and MCI specifically, in real-world contexts which will ultimately provide implications for person-centered lifestyle interventions in PLWH. Thus, the proposed study is likely to stimulate novel ADRD prevention research that will have a long-term impact on the health and quality of life of those PLWH at risk for ADRD.